Anonymous-0
Well-known Member
Guys -
Recently purchased 1939 F-20 has a missing problem. Every 1-5 seconds, the engine misses several firings in a row, then resumes with no hesitation/coughing or smoking. Not like a spark plug missing occasionally , but someone turning off & on the engine. Diagnosis has revealed these clues:
1) Each time the engine misses, a "gasp" can be heard from the carburator with the air filter hose removed.
2) Compression tests show dry results at 55-60, and wet results 55-60, across the board.
3) Spark plugs are clean & set right. Wires are almost new. Cleaned the fiber gear in the mag an cleaned the distributor brushes. The fiber gear does have about a 1/16" groove created by the brushes.
4) Carb has been adjusted lean & rich with little change.
5) More predominant at higher speeds. Less predominate at slow speed and spark retarded.
6) Fresh gasoline didn't help.
7) Engine starts right up after a crank or two.
I'm thinking a sticky intake valve or two.
Your thoughts ?
Recently purchased 1939 F-20 has a missing problem. Every 1-5 seconds, the engine misses several firings in a row, then resumes with no hesitation/coughing or smoking. Not like a spark plug missing occasionally , but someone turning off & on the engine. Diagnosis has revealed these clues:
1) Each time the engine misses, a "gasp" can be heard from the carburator with the air filter hose removed.
2) Compression tests show dry results at 55-60, and wet results 55-60, across the board.
3) Spark plugs are clean & set right. Wires are almost new. Cleaned the fiber gear in the mag an cleaned the distributor brushes. The fiber gear does have about a 1/16" groove created by the brushes.
4) Carb has been adjusted lean & rich with little change.
5) More predominant at higher speeds. Less predominate at slow speed and spark retarded.
6) Fresh gasoline didn't help.
7) Engine starts right up after a crank or two.
I'm thinking a sticky intake valve or two.
Your thoughts ?
), slapping on new rings, removing a few shims on the rods while replacing everything, and Wala. Not perfect, but it did reclaim some compression.